“Disc” vs. “disk”

December 13th, 2009

Q: My dictionary says “disk” and “disc” are simply variant spellings of the same word. But I’ve run across a technical article from Apple that asserts “disc” refers to optical media while “disk” refers to magnetic media. Have you ever heard of this distinction?

A: It’s true that “disc” is a variant spelling of “disk,” but Apple is technically right. Each spelling has marked out its own territory in the technological wilderness, though many non-techies seem to be unaware of the distinction.

As Apple’s support site says, discs are “optical media, such as an audio CD, CD-ROM, DVD-ROM, DVD-RAM, or DVD-Video disc,” while disks are “magnetic media, such as a floppy disk, the disk in your computer’s hard drive, an external hard drive.”

If you’re like me, you may find the optical-vs.-magnetic distinction hard to remember. When in doubt, I go to a dictionary or to The New York Times Manual of Style and Usage, which has a helpful entry:

Either way you spell it, the word entered English in 1664 when it meant a round, flat surface. It was borrowed from the Latin discus, which came from the Greek diskos. So should we go with the Romans and spell it “disc” or with the Greeks and spell it “disk”?

The dictionaries I usually consult – The American Heritage Dictionary of the English Language (4th ed.), Merriam-Webster’s Collegiate Dictionary (11th ed.), and the Oxford English Dictionary – all say that in general “disc” is a variant spelling of “disk.”

The OED (under its entry for “disc, disk”) adds: “The earlier and better spelling is disk, but disc is now the more usual form in British English,” except in the computing sense, “where disk is commoner as a result of US influence.”

However, further examination sheds a little more light.

Merriam-Webster’s has this as one definition of “disk”: “a round flat plate coated with a magnetic substance on which data for a computer is stored.” But it says that an “optical disk” (like a “videodisc” or a “CD”) is usually spelled “disc.”

And American Heritage, under its entry for “compact disk,” has an extensive usage note that I’ll quote in its entirety (I’ll add paragraphing to make it easier to read):

“When new words come into the language, they often have different forms for a period until one form wins out over the others. There are occasions when competing forms remain in use for a long time. The word disk and its descendant compound compact disk represent good examples of this phenomenon.

“Disk came into English in the mid-17th century and was originally spelled with a k on the model of older words such as whisk. The c-spelling arose a half century later as a learned spelling derived from the word’s Latin source discus. Both disc and disk were used interchangeably into the 20th century, with people in Britain tending to use disc more often, and Americans preferring disk.

“The spellings also began to be sorted out by function. Late in the 19th century, for reasons that are not clear, people used disc to refer to the new method of making phonograph recordings on a flat plate (as opposed to Edison’s cylindrical drum). In any case, the c-spelling became conventional for this sense, which is why we listen to disc jockeys and not disk jockeys.

“In the 1940s, however, when American computer scientists needed a term to refer to their flat storage devices, they chose the spelling disk, and this became conventionalized in such compounds as hard disk and floppy disk. When the new storage technology of the compact disk arose in the 1970s, both c- and k-spellings competed for an initial period. Computer specialists preferred the familiar k-spelling, while people in the music industry, who saw the shiny circular plates as another form of phonograph record, referred to them as compact discs.

“These tendencies soon became established practice in the different industries. This is why we buy compact disks in computer stores but get the same storage devices with different data as compact discs in music stores. Similarly, the computer industry created the optical disk, the format that the entertainment industry used to create the videodisc.”